1. Field of the Invention
The present invention relates to a laser beam emitting unit which serves as a fundamental component of a scanning optical system incorporated in, e.g., a laser printer.
2. Description of the Related Art
A laser beam emitting unit which serves as a fundamental component of a scanning optical system incorporated in, e.g., a laser printer is known in the art. Such a laser beam emitting unit is provided with a base plate to which a laser diode is fixed, and a lens holder which is fixed to the base plate and holds a collimating lens which collimates a laser beam emitted from the laser diode.
Formerly, the lens holder is fixed to the base plate so that through holes formed on the lens holder and corresponding through holes formed on the base plate are aligned and so that set screws are screwed into these aligned through holes.
According to such a conventional fixing manner, since the relative position between the lens holder and the base plate is determined by bringing the through holes of the lens holder into alignment with the through holes of the base plate, all the through holes must be formed with an extremely high degree of precision. This is a troublesome task. In addition, the necessity of the set screws for fixing the lens holder to the base plate increases assembling costs.
An object of the present invention is to provide a laser beam emitting unit which is characterized in that the lens holder and the base plate can be fixed to each other while being precisely positioned relative to each other with a high degree of precision and with easy of assembly.
To achieve the object mentioned above, according to an aspect of the present invention, a laser beam emitting unit is provided, including a laser diode, a collimating lens upon which a laser beam emitted by the laser diode is incident, a base plate to which the laser diode is fixed, a lens holder which holds the collimating lens, and a holder support plate via which the lens holder is fixed to the base plate. The holder support plate includes a flat portion which faces the base plate with a gap between the flat portion and the base plate, and at least two leg portions which extend from the flat portion to the base plate in a direction substantially perpendicular to the flat portion. Each of the at least two leg portions includes a claw portion which is deformed to be fixed to the base plate, wherein the gap is maintained between the flat portion and the base plate.
Preferably, the base plate includes at least two receiving portions which receive the at least two leg portions, respectively.
Preferably, the at least two receiving portions include at least two recessed portions in which the at least two leg portions are respectively fitted.
Preferably, each of the at least two leg portions includes an engaging member having a contacting surface which is in contact with the base plate, and a projecting portion which extends from the engaging member to be fitted in corresponding one of the at least two recessed portions, the claw portion being formed on the projecting portion.
Preferably, the base plate has a substantially rectangular shape, the at least two receiving portions including at least one pair of receiving portions respectively formed on opposite sides of the base plate to be opposed to each other.
Preferably, the projecting portion has a substantially U-shape, and includes a projecting base, the claw portion, and a recessed portion formed between the projecting base and the claw portion, and wherein the lens holder is fixed to the base plate by bending the claw portion along a surface of the base plate so that the engaging member and the projecting base hold a portion of the base plate therebetween.
Preferably, the following condition is satisfied:
Ze less than Z5 less than Zt; wherein xe2x80x9cZ5xe2x80x9d represents a thickness of the base plate; xe2x80x9cZtxe2x80x9d represents a distance from a plane including the contacting surface to a first point on a surface of the claw portion in the vicinity of a tip of the claw portion, in the direction substantially perpendicular to the flat portion; and xe2x80x9cZexe2x80x9d represents a distance from the plane to a second point on a surface of the claw portion in the vicinity of the root of the claw portion, in the direction substantially perpendicular to the flat portion.
Preferably, the holder support plate is made of a metal.
Preferably, the projecting base is fitted in corresponding one of the at least two recessed portions with a minimum clearance.
Preferably, the claw portion includes an inclined engaging surface provided on the claw portion opposing the projecting base, the lens holder being fixed to the base plate with the engaging surface in contact with the surface of the base plate.
Preferably, the lens holder is fixed to the holder support plate via at least two set screws, a through hole being formed on the base plate so that a screw driver is accessible to one of the at least two set screws through the through hole.
According to another aspect of the present invention, a laser beam emitting unit is provided, including a laser diode, a collimating lens upon which a laser beam emitted by the laser diode is incident, a base plate to which the laser diode is fixed, and a holder support plate which is fixed to the base plate and supports the collimating lens. The base plate includes at least two recessed portions which define a fixing position of the holder support plate relative to the base plate. The holder support plate includes a flat portion which faces a front surface of the base plate with a gap between the flat portion and the base plate, and at least two leg portions which extend from the flat portion to the base plate in a direction substantially perpendicular to the flat portion to be associated with the at least two recessed portions. Each of the at least two leg portions includes an engaging member which is in contact with the front surface of the base plate, and a projecting portion which extends from the engaging member to be fitted in corresponding one of the at least two recessed portions, a claw portion being formed on the projecting portion, the claw portion being deformed to be fixed to a rear surface of the base plate with the gap being maintained between the flat portion and the base plate.
According to another aspect of the present invention, a laser beam emitting unit is provided, including a base plate to which a laser diode is fixed, a lens holder which holds a collimating lens through which a laser beam emitted by the laser diode is collimated, and a holder support plate positioned between the base plate and the lens holder to fix the lens holder to the base plate via the holder support plate. The holder support plate includes a flat portion which faces the base plate with a gap between the flat portion and the base plate, and a pair of leg portions which extend from the flat portion in a direction substantially perpendicular to the flat portion to be engaged with the base plate. Each of the pair of two leg portions includes a claw portion which is deformed to be fixed to the base plate.
The present disclosure relates to subject matter contained in Japanese Patent Application No.2000-321396 (filed on Oct. 20, 2000) which is expressly incorporated herein by reference in its entirety.